With the development of nanotechnology and ultra-precision measuring technologies, ultrahigh vacuum technologies have been emphasized. Surfaces of semiconductors are subject to pollution by gas molecules. In contrast, by maintaining semiconductors in an ultrahigh vacuum below about 10−7 Pa, the surfaces of semiconductors can be kept clean. And pumps such as an ion pump are used to maintain an ultrahigh vacuum.
As shown in FIGS. 4(A) and 4(B) in Japanese Patent Application Laid-Open No. H9-27294, for example, conventional ion pumps have arranged tabular permanent magnets so as to face each other in parallel across a cuboid container. For this reason, the magnetic fields are unidirectional, and the spaces in the ion pumps have not been able to be effectively utilized.
In order to solve such a problem, “an ion pump comprising a first cylindrical electrode and a second cylindrical electrode in its circumference both arranged concentrically in a cylindrical casing, characterized in that a radial electric field generation means among each cylindrical surface of the said second cylindrical electrode, the first cylindrical electrode and the casing, and a magnetic field generation means parallel to the axis of the said first cylindrical electrode and the second cylindrical electrode are provided in the cylindrical casing” is disclosed in claim 1 in Japanese Patent Application Laid-Open No. H9-27294 (see Patent Document 1 below).
Furthermore, “a sputter ion pump comprising an anode electrode and a cathode electrode arranged in a vacuum chamber, wherein high voltage is applied between the anode electrode and cathode electrode so that electrons are spirally moved by means of a magnetic field, residual gas molecules are collided with electrons that are spirally moving and are ionized, and the ionized molecules sputter the cathode electrode to adsorb onto the surfaces of the anode electrode or the like, thereby performing an evacuation, characterized in that the cylindrical section of the vacuum chamber wall is formed to have a convex or concave cross-sectional profile, permanent magnets each having the same shape and character are located in the direction of the same magnetic pole in each concave portion outside the convex or concave cross-sectional profile, anode electrodes each of which is cylindrical are located apart from the vacuum chamber wall in each concave portion inside the convex or concave cross-sectional profile, the cylindrical portion of the vacuum chamber wall is constituted as a cathode electrode, a cylindrical magnetic shield member equipped with an exhaust hole circumferentially is arranged concentrically with the plurality of permanent magnets and the anode electrodes, and the plurality of permanent magnets and the anode electrodes are arranged at equal intervals axially opposite one another.
However, such ion pumps need to use many insulators such as ceramics in order to obtain insulation between electrodes. For this reason, there is a problem that gases are emitted from ceramics etc., lowering a degree of vacuum. There is also a problem that such ion pumps do not have enough strength.
Furthermore, such ion pumps are large and heavy, and their power consumption is also large. Therefore, there is a problem that once the conventional ion pumps are located they cannot be moved easily.    [Patent Document 1] Japanese Patent Application Laid-Open No. H9-27294    [Patent Document 2] Japanese Patent Application Laid-Open No. 2001-332209